This application claims priority pursuant to Title 35 U.S.C. § 119 to EP Application No. 03024646.6 filed Oct. 27, 2003 and EP Application No. 04024492.3 filed Oct. 14, 2004.
The invention relates to a screw connection device for connecting the flared ends of two pipes. The term “screw connection device” or “connector” comprises the device elements which are required for connecting the ends of the two pipes. The invention relates in particular to a screw connection of pipes which are used in the field of hydraulics, or which are used as brake lines in motor vehicles.
From practical application, a screw connection of two pipes is known in which the end of one pipe comprises a so-called E-flare while the end of the other pipe comprises an F-flare which is complementary to said E-flare. Both E-flares and F-flares are for example defined in DIN 74234. In the known screw connection, both pipe flares are pushed against teach other with very considerable contact pressure force by means of a screw connection device using a nut and an associated screw. The aim is to achieve a tight connection, or a connection which is tight even at high pressure, of the pipe ends. However, this screw connection known from the state of the art has some undesirable disadvantages. When forming the E-flare to one of the pipe ends, this pipe end, at least in certain regions, is plastically deformed to a relatively extensive degree. Because of solidification as a result of cold forming, a negative influence results in relation to the longevity of the formed connection. Such negative influence comes to bear in particular in the case of mechanical loads on the screw connection, for example as a result of exposure to vibration. Furthermore, when the screw connection is being established, at the end of the screwing process, one or both of the pipe ends rotates/rotate as well. Frequently, undesirable rotation of a pipe end relative to the screw connection device also occurs. Since the pipes are usually fixed at their ends which are opposite the screw connection, pipe torsion occurs in such an arrangement. Such pipe torsion exerts torque on the screw connection, with said torque supporting a loosening of the screw connection. For this reason, in practical application the screw connection or the screw arrangement is tightened beyond its limit. If, at the time of establishment of the screw connection, the pipes are rotated in relation to each other, damage to the sealing surfaces can occur as a result of mutual friction between the two pipe flares. It is understood that this is disadvantageous. In summary, the known screw connection can be improved.
In contrast to the above, it is the object of the invention to provide a screw connection or a screw connection device of the type mentioned in the introduction with which connection or connection device, in a simple way, a connection of the two pipe ends can be released which is tight, or tight at high pressure, in the long term, and which avoids the disadvantages explained above, and with which connection or connection device in particular undesirable rotation of the pipe ends can be prevented or minimized during production of the screw connection.
This object is met by a screw connection device according to the invention for connecting the flared ends of two pipes, wherein a distance element is provided which at a first end comprises a first positive-fit recess for positive-fit accommodation of the flare at the end of a (first) pipe, and at a second end comprises a second positive-fit recess for positive-fit accommodation of the flare at the end of the other (second) pipe, wherein furthermore a nut is provided for accommodating the one pipe end, in which nut the distance element in the connected state has been inserted such that the flare of the pipe end accommodated by the nut grips the associated positive-fit recess of the distance element and wherein furthermore a screw for accommodating the other pipe end is provided, with the accommodated pipe end of said screw in the connected state being screwed into the nut such that the flare of the pipe end accommodated by the screw grips the associated positive-fit recess of the distance element, and wherein the nut and/or the pipe flare of the pipe end which in the connected state is accommodated in the nut comprise positive-fit elements, which positive-fit elements are designed such that the accommodated pipe end is secured against rotation relative to the nut.
The term “in the connected state” refers to the state when the screw connection between the two flared pipe ends has been established. The invention relates to a screw connection device comprising a nut, a screw and a distance element, or the invention relates to a screw connection device which essentially comprises the nut, the screw and the distance element. However, the invention also covers the screw connection unit which comprises the nut, the screw, the distance element and the two pipe ends which are to be connected.
According to a first preferred embodiment of the invention, the nut comprises positive-fit elements on the inside, while the pipe flare of the pipe end which in the connected state is accommodated in the nut comprises complementary positive-fit elements, while in the connected state the interior positive-fit elements of the nut engage the complementary positive-fit elements on the pipe flare. In this way, the accommodated pipe end is effectively secured against rotation relative to the nut. According to one embodiment, the positive-fit elements are notches provided in the nut, which notches are preferably aligned radially. In this arrangement, the complementary positive-fit elements on the pipe flare are then expediently designed as corresponding projections which can engage the notches on the nut so as to provide positive fit. According to another embodiment, the complementary positive-fit elements of the pipe flare can also be designed as notches, in which case the positive-fit elements on the nut are preferably in the form of projections or webs which can engage the notches on the pipe flare so as to provide positive fit. According to the invention, the depth of the notches or the height of the projections or webs is selected such that when there is positive fit the accommodated pipe end is secured against rotation relative to the nut.
According to another preferred embodiment of the invention, only the nut comprises interior positive-fit elements, which positive-fit elements are designed such that when they establish the screw connection they cut into the pipe flare of the pipe end which in the connected state is accommodated in the nut, so that complementary positive-fit elements form in the pipe flare. In this embodiment the pipe flare does not have any complementary positive-fit elements to start with, but instead, these complementary positive-fit elements are only formed by the corresponding pressing action, at the time the screw connection is made, due to the action of the positive-fit elements onto the pipe flare. Expediently, the positive-fit elements on the nuts are projections or webs which can cut into the pipe flare. It is within the scope of the invention for the material for the pipe flare to be selected accordingly, so that such cutting into the pipe flare and the formation of complementary positive-fit elements is easily possible.
It is within the scope of the invention for the distance element to be a sealing distance element. In other words, each positive-fit recess of the distance element comprises a sealing surface or sealing surfaces which comes/come to rest against a complementary sealing surface of the associated pipe flare. Furthermore, it is within the scope of the invention for the nut to comprise an internal thread and for the screw to comprise a complementary external thread with which it engages the internal thread of said nut in the connected state. The nut accommodates a first pipe end. It is the pipe end which, when the screw has not yet been inserted in the nut, is already accommodated in the nut. When the screw with the accommodated second pipe end has been inserted in the nut, the nut also encompasses the second pipe end accommodated in the screw.
According to a particularly preferred embodiment which assumes particular importance within the scope of the invention, at least one positive-fit recess, and particularly preferred both positive-fit recesses of the distance element is/are designed for positive-fit accommodation of a flare at the associated pipe end, with said flare comprising a cone-shaped flange face on the outside of the pipe, wherein the associated cone tapers off towards the face end of the pipe end. The positive-fit recess of the distance element comprises a corresponding complementary cone-shaped complementary flange face on the inside. It is within the scope of the invention for at least one positive-fit recess, particularly preferably for both positive-fit recesses of the distance element to be designed for positive-fit accommodation of an F-flare at the associated pipe end. At both ends, the distance element thus comprises at least one, preferably two, positive-fit recesses which is/are complementary to an F-flare.
It is thus within the scope of the invention for both pipe ends which are to be connected to comprise an F-flare. In the connected state, the F-flare of the first pipe end is thus adjoined by the first positive-fit recess of the distance element, while at the opposite end of the distance element, the F-flare of the second pipe end grips the second positive-fit recess of the distance element. According to a preferred embodiment, the connection F-flare/distance element/F flare takes place without the incorporation of any further elements. It is also within the scope of the invention that the distance element faces be complimentary to SAE flares. Also, one face of the distance element could be complimentary to an F-flare and the other could be complementary to an E-flare.
According to one embodiment of the invention, in the connected state, the distance element is inserted in an accommodation aperture of the nut. In this embodiment, the distance element is not held in the nut by a screw connection, but instead is only inserted with positive fit into the accommodation aperture of the nut. Expediently, in this arrangement the distance element is held by at least one knob provided on the surface or interior surface of the accommodation aperture. Preferably, the distance element is inserted into the accommodation aperture by way of the knob, literally clicking into place behind the knob. According to a preferred embodiment, several such knobs are distributed on the interior circumference of the accommodation aperture. It is within the scope of the invention for the accommodation aperture of the nut to be cylindrical in shape.
According to another preferred embodiment of the invention, the accommodation aperture of the nut comprises an internal thread and the distance element comprises an external thread which is complementary to the internal thread. According to this embodiment, in the connected state the distance element is screwed into the accommodation aperture of the nut. The distance element is thus fixed in the accommodation aperture of the nut by means of a screw connection.
It is within the scope of the invention for the accommodation aperture of the nut to be provided both for accommodation of the distance element and for accommodation of the screw. The screw is screwed in with its external thread engaging the internal thread of the accommodation aperture.
It is furthermore within the scope of the invention for the nut to comprise an accommodation channel of reduced diameter when compared to the diameter of the accommodation aperture, with said accommodation channel being provided for accommodating the one (first) pipe end. This (first) pipe end thus reaches through the accommodation channel of the nut. Expediently, the screw also comprises an accommodation channel for accommodating the other (second) pipe end.
It is within the scope of the invention for the nut to comprise a stop face which in the connected state grips from the rear the flare of the (first) pipe end and accommodated in the nut. Expediently, the stop face is arranged at the transition between the accommodation channel and the accommodation aperture of the nut. It is furthermore within the scope of the invention for the screw to comprise a face which grips from the rear the pipe flare of the (second) pipe and accommodated in the screw.
As already outlined above, it is within the scope of the invention for the nut to comprise interior positive-fit elements for engagement with complementary positive-fit elements on the pipe flare of the pipe end which is accommodated in the nut, wherein the complementary positive-fit elements can already be present in the pipe flare, or alternatively, can be generated during establishment of the screw connection by cutting positive-fit elements into the nut. Expediently, the positive-fit elements of the nut are provided on the above-mentioned stop face of the nut.
A preferred embodiment of the invention is characterized in that the nut comprises interior positive-fit elements for engaging the complementary positive-fit elements on the pipe flare of the (first) pipe and accommodated in the nut, which positive-fit elements or complementary positive-fit elements are designed such that the accommodated pipe end is secured against rotation relative to the nut. It is within the scope of the invention for these positive-fit elements to be provided on the stop face of the nut. In a preferred embodiment, these positive-fit elements can be teeth or projections which engage corresponding retaining notches on the flare of the accommodated pipe end.
It is within the scope of the invention for the distance element on at least one positive-fit recess, preferably on both positive-fit recesses, to comprise a surface which is designed such that the torque provided by one pipe end is safely transferred. The surface of the positive-fit recess can for example be a profiled surface. In this connection it is within the scope of the invention for the surface of the positive-fit recess to comprise positive-fit elements for engaging the complementary positive-fit elements on the flange face of the flare of the associated pipe end.
As a result of the last-mentioned embodiments according to the invention, any rotation of the pipe ends relative to the distance element or relative to each other can effectively be suppressed.
The invention is based on the recognition that with the screw connection device according to the invention, in a simple and economical way, a connection can be established which is tight, or tight at high pressure, in the long term. In particular, during operation of the screw connection device no disadvantageous impairment of the sealing surfaces takes place. With the screw connection device according to the invention, rotation of the pipes to be connected, relative to each other, during screwing together can be prevented. The invention is in particular based on the essential recognition that is this context it is important that rotation of the pipe accommodated by the nut relative to the nut be prevented. As a result of this, the pipes or the screw connection device can easily be installed, for example in a motor vehicle.
Because rotation of the pipes relative to the distance element is avoided, damage to the sealing surfaces as a result of friction can be prevented. In particular, friction between the pipe flare on the side of the screw and the distance element can be kept relatively high by means of a suitable geometric shape of the distance element. If this friction between the flare on the side of the screw and the distance element exceeds the friction between the screw and the rear of the flare, when the screw connection is established the screw will rotate relative to the pipe accommodated therein. Rotation of the two pipes relative to each other is thus suppressed and any associated undoing moment can thus also be prevented.
Below, the invention is explained in more detail by means of drawings which shows examples of embodiments of the invention.